This invention relates to drive shafts used in acoustic imaging catheters.
Acoustic imaging catheters are used in medicine to visualize the internal conditions of the body, such as the condition of the walls of the vascular system. The imaging catheters comprise a transducer probe attached to the end of a flexible rotating drive shaft. The drive shaft is used to insert the transducer into the body, and to rotate the transducer at high speed to produce a 360 degree image.
One drive shaft that has been employed comprises two cross-wound, multifilar stainless steel interlocking coils, as described in Crowley et al., U.S. Pat. No. 4,951,677, incorporated by reference.
It is important that the drive shaft be flexible enough to pass through tortuous passages in the body. The drive shaft should also have one-to-one rotational fidelity between its proximal and distal ends to avoid image smearing. Acoustic imaging is made more powerful when the drive shaft, and consequently the catheter itself, has a very small outer diameter, enabling it to penetrate into more restrictive regions of the body.